1. Field of the Invention
The present invention relates to a technique of spot welding.
2. Description of Related Art
Spot welding is one of a welding process for joining metals, applying an electrical current to a workpiece to melt the metals by the heat obtained from resistance. The conventional spot welding apparatus includes a welding gun for holding the workpiece and applying current thereto, and a transformer for applying a high electrical current to the welding gun. In the case that spot welding is performed to a large workpiece such as a vehicle body, the welding gun is mounted on an industrial robot.
For example, JP 2006-088160 A discloses a spot welding apparatus enabled to weld at an accurate welding position. The spot welding apparatus of JP 2006-088160 A determines whether the welding position is in the predetermined range by comparing a precise measurement data of a CAD data with an actual measurement data of the welding position obtained by a coordinate measuring machine.